The cause of a mass fish kill in Chartiers Creek in Washington and Allegheny counties remains under investigation.
The state Department of Environmental Protection, which, with the Pennsylvania Fish and Boat Commission, is investigating the death of thousands of fish along a 10-mile stretch of Chartiers Creek, suspects a pesticide or herbicide is responsible, but expects lab results by July 30.
Sam Carroll, chairman of the Washington County Watershed Alliance, estimates tens of thousands of fish, including small mouth bass, died in the event.
“It’s very unfortunate that this happened,” said Carroll, noting the watershed alliance has spent more than 20 years working to improve water quality impacted by industry and other issues to promote the creek for fishing, kayaking and recreation.
“We’ve put in tons of man hours over the last 20 years to get the creek cleaned up. It’s amazing to think how far along it’s come. In the 1950s the creek ran black, and the only thing that could live was carp. Now, there is a diversity of species and the size of some of the fish is impressive.”
The fish kill was reported on July 15. It encompassed a 10-mile stretch that started from Valley Brook Road in Peters Township and continued downstream, the DEP said.
Carroll said the die-off appears to be a one-time event “where chemicals possibly were released; it went through the stream and killed everything on its way to the Ohio River, where it was diluted.”
“It really was a lot of fish,” said Carroll.
Carroll, who visited the site on several occasions in recent days, said some minnows, along with frogs and other species, survived.
Carroll said fish will move from upstream and downstream into the stretch of area impacted, but estimates it could take months to years for the level of wildlife to return.
“But it’s important to point out that, as impactful as this was, there is a lot of hope,” said Carroll.
The watershed alliance, in cooperation with groups including the Upper Chartiers Creek Watershed Association in Washington County and the Lower Chartiers Creek Watershed Association in Allegheny County, will continue to monitor the recovery of the fish population and work to maintain the creek’s viability.